1. Field of the Invention
The present invention relates to a lane recognition apparatus suitable for recognizing a lane from input images captured from a visual sensor mounted on a vehicle at a fixed time interval, in particular, for recognizing dotted line lane boundaries, etc.
Priority is claimed on Japanese Patent Application No. 2005-078988, filed Mar. 18, 2005, the content of which is incorporated herein by reference.
2. Description of Related Art
An apparatus is known which recognizes lane boundaries marked on a road surface or lane markers buried in a road surface from a visual sensor mounted on a vehicle to detect the position and the direction of the driver's vehicle. For example, a forward vehicle recognition apparatus is disclosed which includes: a white line preprocessing part for extracting edges in an input image; a white line recognition part for recognizing solid white lines of a traveling lane; a preprocessing part for extracting edges after time series smoothing of the input image; and a forward vehicle recognition part for recognizing a forward vehicle, in order to reduce the computational cost in image processing (see Japanese Unexamined Patent Application, First Publication No. H09-259287 (reference 1)).
Furthermore, a Hough transform method for lane detection is known which performs time series smoothing, mixing an output at the preceding time with an input at a rate (α)(τ(i)=αx(i)+(1−α)τ(i−1) τ: output x: input i: time), and detecting a lane (see J. McDonald, J. Franz and R. Shorten. Application of the Hough Transform to Lane Detection in Motorway Driving Scenarios. Proceedings of the Irish Signals and Systems Conference, 2001 (reference 2)).
According to the art disclosed in the above-described reference 1, time series smoothing is performed before detection of lines. However, the accurate smoothing method is not disclosed therein, and the art relies the line detection on the weighing the detection results from the far side based on the detection outcomes from the near side. Therefore, detection of dotted line lane boundaries is considered to be impossible.
Furthermore, the detection possibility of dotted line lane boundaries is not disclosed in the above-described reference 2. While the detection may be possible to a certain degree, detection performance is considered to be low due to the art's assumption that a boundary marking is continuous throughout image sections aligned from near to far.